1. Field of the Invention
The present invention relates to a magnetic head of sliding type used in a high recording density floppy disk drive having downward compatibility, and a method for producing the same.
2. Description of the Related Art
With a trend towards a higher recording density of a floppy disk drive increasing from 120 MB to 260 MB, the rotational speed of a spindle has accordingly increased from 740 rpm to 1500 rpm, and the recording frequency has also increased to approximately 7 MHz. In the trend, the traceability of magnetic cores, especially for a high recording density, along recording media is increasingly becoming important for achieving stable electromagnetic conversion characteristics. The traceability, i.e., facility to identify and follow a track in a repeatable manner, depends upon the contact between an operating gap of a magnetic core and a signal recording surface of a recording medium.
As the inventors have disclosed in Japanese Patent Application No. 2000-105863, a slider of a conventional magnetic head having downward compatibility has a construction as shown in FIGS. 6A and 6B, wherein FIG. 6A is a front view and FIG. 6B is a sectional view taken along the line A-Axe2x80x2. Such a slider 1 includes a magnetic core 4 having an operating gap for a standard recording density, a magnetic core 3 having an operating gap for a high recording density, and an outrigger 2 having substantially rectangular slots 8 and 9 for inserting the respective magnetic cores into. The magnetic core 3 for a high recording density having a spacer 5 superposed thereon is inserted into the slot 8 in such a manner that a side of the magnetic core 3 touches a wall of the slot 8.
Furthermore, the magnetic core 4 having an operating gap for a standard recording density is inserted into the slot 9. The two slots 8 and 9 are filled with a sealing glass 7 thereby sealing up the magnetic cores 3 and 4, and the spacer 5.
The thickness of the magnetic core 4 having an operating gap for a standard recording density presents no problem in maintaining the accuracy of a die for making the slot 9. However, it is difficult to maintain the accuracy of a die for making the slot 8 to precisely fit the magnetic core 3 because the thickness of the magnetic core 3 is approximately 80 xcexcm. For this reason, the slot 8 is formed to have a width larger than the thickness of the magnetic core 3, and the high recording density magnetic core 3 and the spacer 5 superposed thereon are inserted together into the slots in such a manner that only the magnetic core 3 touches a wall of the slot 8, thereby positioning the high recording density magnetic core 3 with respect to the slot 8.
The surfaces of the magnetic core 4 having an operating gap for a standard recording density, of the magnetic core 3 having an operating gap for a high recording density, and of the spacer 5 superposed on the magnetic core 3 are brought into contact with a signal recording surface of a recording medium.
A slider with such conventional magnetic heads 60 and 61 arranged vertically is shown in FIG. 7 showing a schematic construction. The magnetic heads 60 and 61 shown in FIG. 7 have respective sliders 1 that slide against a magnetic recording medium (not shown). A standard recording density magnetic core 4 having an operating gap is inserted in one substantially rectangular slot 9 formed in each of the sliders 1 and sealed up by a sealing agent, such as a glass 7 or the like.
A high recording density magnetic core 3 having an operating gap and having a spacer 5 superposed thereon is inserted in another substantially rectangular slot 8 and sealed up with a sealing agent, such as a glass 7 or the like. There are also included a back yoke 50 made of a magnetic material and joined to the magnetic cores 3 and 4 to form a closed magnetic path together with the slider 1, and recording and reproducing coils 40 and 30 wound around pillars 51 and 53, respectively, of the back yokes 50. The magnetic heads 60 and 61 are vertically disposed so as to sandwich a magnetic recording medium (not shown) as illustrated in FIG. 7.
However, as illustrated in FIG. 6A and FIG. 6B, a present rail width W1 does not provide a satisfactory traceability to successfully deal wit a higher recording density. The rail width must be reduced to bring a magnetic core into further proper and stable contact with a signal recording surface of a recording medium. Referring to FIG. 6, if, for example, the rail width in the present construction is reduced to W2, then the sealing glass 7 on side surfaces of the magnetic core 3 and an outrigger 2 have to be simultaneously processed (machined). These two components have different processing conditions from each other, and in case the processing conditions for the outrigger 2 are met, the glass portion is chipped. And if the chipping can-not be removed at a process for polishing the sliding surface of the slider 1, then the chipping will scratch a recording medium, causing errors when a drive is operated.
If the rail width is further reduced to W3, shown in FIG. 6, then a recording medium, which is flexible, deforms and warps in the vicinity of the side surfaces of the magnetic core, adversely affecting the contact between the recording medium and a rail surface.
As shown in FIG. 7, in the upper and lower magnetic heads 60 and 61, the rail surfaces of the standard recording density magnetic cores 4 oppose the rail surfaces of the high recording density magnetic core 3 with a recording medium therebetween. Therefore, the width of each rail must be set so as to ensure reliable and stable contact between a recording medium and the opposing magnetic cores when a load pressure is applied to a magnetic head installed in a drive.
On the other hand, as previously mentioned, the rail width of the high recording density magnetic core 3 must be reduced as much as possible to enhance the traceability for magnetic disks of a higher recording density. This requirement conflicts with the requirement that the rail width of the high recording density magnetic core 3 preferably be equal to the rail width of the standard recording density magnetic core 4 in order to ensure reliable and stable contact between a recording medium and the opposing magnetic cores.
The present invention has been made in view of the above, and it is an object of the present invention to provide a magnetic head that exhibits good traceability without giving damages to itself and a magnetic disk.
To this end, according to one aspect of the present invention, in a magnetic head including a slider which comprises a plurality of magnetic cores having respective operating gaps for a standard recording density and a high recording density and an outrigger having a plurality of substantially rectangular slots for inserting the respective magnetic cores in, which slides against a magnetic recording medium, and in which one magnetic core for a high recording density having a spacer superposed thereon is inserted in one of the slots in such a manner as to touch a wall of the slot, the slider includes a rail surface which has a groove passing longitudinally through the spacer substantially at the center of its thickness and reaching both lengthwise ends of the slider, and which slides against the magnetic recording medium.
With this arrangement, the magnetic head maintains stable contact between magnetic cores and a recording medium, improves the traceability of a high recording density core, and stabilizes electromagnetic conversion characteristics.
In a preferred form of the magnetic head in accordance with the present invention, the spacer is formed of the same material as that of the outrigger.
This arrangement enables the spacer and the outrigger to have the same processing conditions, so that chipping of a glass portion can be prevented. Hence, a recording medium will not be scratched, and the occurrence of errors can be suppressed while a drive is in operation.
In another preferred form of the magnetic head in accordance with the present invention, the high recording density magnetic core and the spacer superposed thereon are inserted in one of the slots and sealed up with a sealing glass having a thermal expansion coefficient matched with that of the outrigger and the spacer.
This arrangement allows the magnetic head to be set in a predetermined position, and also prevents cracking caused by a difference in thermal expansion coefficient.
According to another aspect of the present invention, there is provided a method for producing a magnetic head including a slider which has a plurality of magnetic cores having respective operating gaps for a standard recording density and a high recording density and an outrigger having a plurality of substantially rectangular slots for inserting the respective magnetic cores in, and which slides against a magnetic recording medium, the method comprising the steps of: inserting one magnetic core for a high recording density and a spacer superposed thereon in one slot formed in the outrigger; inserting another magnetic core for a standard recording density in another slot in the outrigger; sealing the slots with a sealing glass having a thermal expansion coefficient matched with that of the outrigger; setting the slider on a slicer so that a groove with a predetermined width and depth can be cut so as to pass through the spacer substantially at the center of its thickness and to reach both lengthwise ends of the slider; cutting the groove beginning at an end of the slider to form a rail surface; polishing a sliding surface and a rear surface of the slider to a determined dimension and surface roughness: and joining the slider thus finished to a back yoke equipped with coils, then fixing the joint with an adhesive agent.
The method for producing a magnetic head makes it possible to fabricate a magnetic head that maintains stable contact between the magnetic cores and a recording medium, thereby improving traceability of the high recording density core to a recording medium and stabling electromagnetic conversion characteristics.